(i) Technical Field
The present invention relates to semiconductor devices, and more particularly, to a semiconductor device having a silicon nitride film composed of two layers on a gate electrode.
(ii) Related Art
Semiconductor devices using nitride semiconductors are used in, for example, power devices capable of operating at high frequencies and outputting high power. Particularly, FETs (Field Effect Transistors) such as HEMT (High Electron Mobility Transistor) are known as transistors suitable for amplifying in high-frequency or RE bands, which may include microwaves, quasi-millimeter waves, or millimeter waves. Japanese Patent Application. Publication No. 2008-305894 discloses such FETs.
It is known that the current collapse phenomenon takes place in the semiconductor devices using the nitride semiconductors. It is required that the characteristics are not changed by or in test. It is also required that a metal included in the gate electrode does not diffuse into an insulating film.